Abstract: 6-O-Carboxymethyl-D-galactopyranose ( Ⅴ ) was synthesized from D-galactose ( Ⅰ ) through hydroxyl protection, nucleophilic substitution, saponification and deprotection reactions. The structures of the products of each synthesized step were characterized with IR, ¹H NMR and ¹³C NMR spectra. The moisture retentivity of product Ⅴ was tested on tobacco and compared with that of D-galactose, propylene glycol, glycerin and sorbierite respectively. The results showed that:1) The synthesized compound Ⅴ was the target product, the final total yield was 50.8%; 2) The moisture retentivity of Ⅴ was better than that of D-galactose, propylene glycol, glycerin and sorbierite.